Alkaline accumulators and lead-acid batteries are most important power sources since a long time ago. Both have advantages and disadvantages and the two battery types cannot be said to compete on the market.
The alkaline accumulators are much more expensive to manufacture than the corresponding lead-acid batteries since the positive electrodes contain expensive electrode materials, frequently nickel oxide, but sometimes also silver oxide. The today dominating embodiment of alkaline accumulators does furthermore use cadmium as negative electrode material, which is expensive and poisonous. Iron has therefore recently attracted attention as negative electrode material in alkaline accumulators.
The lead-acid battery has a bigger market than the alkaline accumulators depending on lower cost and satisfactory performance and life for many applications including traction applications. The lead-acid battery, however, uses heavy electrode and construction materials. The electrolyte in the lead-acid battery, most frequently sulphuric acid, is also consumed in the cell reaction contrary to the case with alkaline accumulators, where the composition of the electrolyte in general does not change during charge and discharge. The theoretically possible energy density for the acid-lead battery is therefore low.
Several new applications put up special requirements on the batteries, for instance traction applications like electric cars and stationary applications like load levelling batteries for power systems. Common features for these new applications are the demands on very low manufacturing costs, high efficiency in the energy conversion, simple design, no maintenance requirements, long life etc. In the traction application a high power and energy density is furthermore desired, which is a less pronounced requirement in the case of load levelling batteries for power grids, where first cost and life and, of course, the conversion efficiency are most important factors. There is, therefore, a need for a battery which combines the good properties of the lead-acid batteries and the alkaline accumulators. The present invention is concerned with such a new battery.